The seas and other natural water reservoirs have provided an abundant and stable supply of sustenance for millennia. In recent years, however, over-fishing, inefficient harvesting practices, and environmental stressors have resulted in the depletion or decline of certain fish populations in many regions. At the same time, an increasing human population, increasing standards of living, and an increasing awareness of the health benefits of seafood have increased the demand for fish and fish product.
Advances in aquaculture in general and fish farming in particular, and improvements in technology have recently been applied to meet world demand for fish product efficiently and at lower costs. Developments in fish farming also reduce the risks associated with over-fishing existing fish populations. In particular, off-shore cultivation systems employing fish cages or fish pens have found some success. Large, submersible fish pens suitable for aquaculture applications are known in the art to aid in the efficient and bio-responsible cultivation of food sources. Fish pens are placed in a natural body of water, such as a lake, river, or ocean, and stocked with young fish or fry, and the fish are typically fed and maintained until they reach maturity. The fish pens provide a habitat and protection for the fish. Fish pens may be used for freshwater or for saltwater aquaculture.
Some conventional fish farming systems provide a pen that is anchored to the ocean floor. In one embodiment, the pen includes four spar buoys with damper plates coupled to the bottom that dampen the buoy motion caused by wave action. The four spar buoys are typically arranged in a rectangular array with a net fastened to the spar buoys to define a box-like enclosure. Anchor lines extend outwardly and downwardly from each spar buoy to support the nets.
While such conventional fish farming pens have significant advantages, they also have limitations. For example, the fish pen is substantially immobile because the enclosed volume is dependent on the spacing of the individual spar buoys.
More recent innovations in fish pens employing a center spar buoy or center cluster of spar buoys are disclosed in U.S. Pat. No. 5,359,962, to Loverich, and in U.S. Pat. No. 5,617,813, to Loverich et al., both of which are hereby incorporated by reference in their entireties. Loverich et al. discloses a mobile pen for growing fish or shellfish having an elongate central vertical spar buoy surrounded by at least one horizontal net-supporting rim assembly with continuous netting extending from an upper end of the spar buoy to the rim assembly and thence to a lower, submerged end of the spar buoy.
However, there remains a need for improvements in fish pen construction. Fish pens are expensive and can be difficult to assemble and install. Access to aquaculture fish pen in situ is challenging due to its off-shore location, netting exterior, and details of construction. It can be difficult to extract fish from the fish pen and to provide treatment to maintain the health of the fish population.